Physics · Science General

Optics and Light Properties

2,019 Questions

Optics and light properties focus on the behavior of light, including reflection, refraction, dispersion, and polarization. This topic also covers the wave nature of light, illumination, and the functioning of optical instruments like microscopes. Questions on these concepts are common in general science sections of SSC, Railways, and State exams.

Reflection and mirrorsRefraction and mediumsLight wave theoriesPolarization and intensity

Optics and Light Properties Questions

Multiple choice physics wave optics huygens wave theory and wavefront wave propagation (huygens' construction) theories on light wave behaviour

Which of the following phenomena can be used to analyse a beam of light into its component wavelength?

  1. Reflection

  2. Refraction

  3. Polarisation

  4. Interference
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
  • Refraction of light is the most commonly observed phenomenon, but other waves such as sound waves and water waves  also experience refraction. 
  • How much a wave is refracted is determined by the change in wave speed and the initial direction of wave propagation relative to the direction of change in speed.
  • Hence refraction is used to analyse a beam of light into its component wavelength
  • Option B is the right answer
Multiple choice physics wave optics huygens wave theory and wavefront wave propagation (huygens' construction) theories on light wave behaviour

Ray optics is valid when characteristic dimensions are

  1. of the same order as the wavelength of light

  2. much smaller than the wavelength of light

  3. much larger than the wavelength of light

  4. of the order of 1 mm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Ray optics is valid when characteristics dimensions are larger than the wavelength of the light, so that rectilinear property of light can be used.

Multiple choice physics wave optics huygens wave theory and wavefront wave propagation (huygens' construction) theories on light wave behaviour

Which experiment seemed to make it clear that light propogates as a wave?

  1. Milikan's oil drop experiment

  2. The Michelson-Morley experiment

  3. Young's double-slit experiment

  4. Fresnel's lens experiment

  5. Lenz's proof of Lenz's law
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Young's double slit experiment 
The double slit experiment is a demonstration that light and matter can display characteristics of both classically defined waves and particles. Moreover it displays the fundamentally probabislistic nature of quantum mechanical phenomena
Multiple choice physics wave optics huygens wave theory and wavefront wave propagation (huygens' construction) theories on light wave behaviour

Indentify the correct statement from the following

  1. Wave nature of light was proposed by Huygen.

  2. The direction of light ray and its wave front are opposite.

  3. Huygen's wave theory could not explain phenomenon of reflection.

  4. A monochromatic ray of light after passing through the prism should be made of one colour only.
Reveal answer Fill a bubble to check yourself
A,D Correct answer
Explanation

Huygen's wave theory: This wave theory was given by Huygens in 1678. According to this theory, a source of light propagates spherical waves in hypothetical.

In optics a ray is an idealized model of light, obtained by choosing a line that is perpendicular to the wavefronts of the actual light, and that points in the direction of energy flow.
Huygen’s wave theory could easily explain reflection, energy transmission, and refraction, but had difficulty explaining the straight line travel of light.
When a ray of monochromatic light would pass through a prism, you would see it refract but it will not disperse as its a beam of single wavelength. When light enters a medium with a different density it bends (refracts). Because white light contains a collection of component colors with varying wavelengths.

Multiple choice physics wave optics huygens wave theory and wavefront wave propagation (huygens' construction) theories on light wave behaviour

The wavefront of a lightbeam is given by the equation $x+2y+3z=c$,(where c is arbitary constant) the angle made by the direction of light with the y-axis is:

  1. ${ cos }^{ -1 }\frac { 1 }{ \sqrt { 14 } } $
  2. ${ cos }^{ -1 }\frac { 2 }{ \sqrt { 14 } } $
  3. ${ sin }^{ -1 }\frac { 1 }{ \sqrt { 14 } } $
  4. ${ sin }^{ -1 }\frac { 2 }{ \sqrt { 14 } } $
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given,

Direction of light, $\vec n=\hat i+2\hat j+3\hat k$
The angle made by the direction of light with y-axis is
$cos\beta=\hat n.\hat j$
$cos\beta=\dfrac{\vec n}{|\vec n|}.\hat j$
$cos\beta=\dfrac{(\hat i+2\hat j+3\hat k).(0\hat i+\hat j+0\hat k)}{\sqrt{(1)^2+(2)^2+(3)^2}}=\dfrac{2}{\sqrt{14}}$
$\beta=cos^{-1}\dfrac{2}{\sqrt{14}}$
The correct option is B.

Multiple choice physics wave optics huygens wave theory and wavefront wave propagation (huygens' construction) theories on light wave behaviour

Coherent sources can be obtained:

  1. only by division of wave front

  2. only by division of amplitude

  3. both by division of amplitude and wave front

  4. none of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Coherent sources can be created by dividing the wavefront (e.g., Young's double slit) or by dividing the amplitude (e.g., thin film interference).

Multiple choice physics wave optics huygens wave theory and wavefront wave propagation (huygens' construction) theories on light wave behaviour

Assertion  $(A):$  Microwaves are better carries of signals than optical waves
Reason  $(R):$  Microwaves move faster than optical waves

  1. Both $A$ and $R$ are true and $R$ is correct explanation of $A$
  2. Both $A$ and $R$ are true and $R$ is not the correct explanation of $A$
  3. $A$ is true but $R$ is false
  4. $A$ is false but $R$ is true
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
A frequency of an optical wave is more than the microwave so optical waves are better canes of the signal, therefore, A is false. In medium (other than vacuum) speed of 0 microwaves 1A greater than optical wave hence R 1A true.
Ans. (D)